Integrated optical sensor

Abstract

An integrated optical sensor for, for example, a (bio)chemical sensor has an optical waveguide ( 2 ) having at least two coupling regions ( 3, 5 ), which are separated by at least one measurement region ( 4 ). A first wave is excited in the waveguide ( 2 ) by the first coupling region ( 3 ) and passes through the measurement region ( 4 ) and the second coupling region ( 5 ). A second wave is excited in the second coupling region ( 5 ) and subsequently interferes with the first wave. Here, the reduction in amplitude of the first wave by the second coupling region ( 5 ) is less than 95%.

1. Integrated-optical sensor, comprising
 An optical waveguide ( 2 ) having at least a first incoupling region ( 3 ), wherein a sensing wave ( 14 ) is excited by a sensing beam ( 12 ), and a second incoupling region ( 5 ), wherein a reference wave ( 15 ) is excited by a reference beam ( 13 ), and an interference signal is created between the sensing wave ( 14 ) and the reference wave ( 15 ), 
 at least one sensing area ( 4 ) located between, and in a direction of the waveguide's mode propagation in line with, the first ( 3 ) and the second ( 5 ) incoupling regions and passed through by the sensing wave ( 14 ), wherein a change of the propagation constant of the waveguide ( 2 ), and thus a phase shift of the sensing wave ( 14 ), occurs depending on the optical environment, 
 at least one detector ( 22 ) for measuring of an interference signal between the sensing wave ( 14 ) and the reference wave ( 15 ),
 wherein at least a part of the sensing wave ( 14 ) passes through the second incoupling region ( 5 ) after the sensing area ( 4 ), and the second incoupling region is constructed such that the ratio of the amplitudes of the sensing wave ( 14 ) in front and behind the second incoupling region ( 5 ) is 20:1 at most, and
 wherein the interference signal is guided within the optical waveguide ( 2 ), and 
 wherein the optical waveguide is a light conduit of solid dielectric material adjacent to another solid dielectric material of lower refractive index. 
 
 
 
     
     
       2. Integrated-optical sensor according to  claim 1 , wherein the ratio of the amplitudes of the sensing wave ( 14 ) in front and behind the second incoupling region ( 5 ) is at most 10:1. 
     
     
       3. Integrated-optical sensor according to  claim 1 , wherein the sensing area ( 4 ) has a length of at least 1000 times the vacuum wavelength of the sensing wave ( 14 ). 
     
     
       4. Integrated-optical sensor according to  claim 1 , wherein the sensing area ( 4 ) comprises at least one adlayer ( 7 ) which binds at least partially at least one substance to be measured and contained in an analyte ( 8 ) being in contact with the adlayer ( 7 ). 
     
     
       5. Integrated-optical sensor according to  claim 4 , further comprising at least one reference sensing area without an additional layer ( 7 ) between the first and second incoupling region ( 3 ,  5 ) for the determination of a background signal. 
     
     
       6. Integrated-optical sensor according to  claim 4 , comprising between the first and second incoupling region ( 3 , 5 ) at least three or at least seven sensing regions having different adlayers ( 7 ) for the parallel measurement of several substances. 
     
     
       7. Integrated-optical sensor according to  claim 1 , wherein all incoupling regions ( 3 ,  5 ) and outcoupling regions ( 6 ), combined designated as coupling regions ( 3 ,  5 ,  6 ), are formed as grating couplers. 
     
     
       8. Integrated-optical sensor according to  claim 7 , further comprising a coherent light source ( 21 ) and illumination optics ( 23 ), wherein the coupling regions ( 3 ,  5 ,  6 ) have a length of only 400 μm, and the light from the light source ( 21 ) is focused at least partially by the illumination optics ( 23 ) onto the incoupling regions ( 3 ,  5 ). 
     
     
       9. Integrated-optical sensor according to  claim 7 , wherein the coupling regions ( 3 ,  5 ,  6 ) comprising grating structures are not in contact with the analyte ( 8 ), and wherein the coupling regions ( 3 ,  5 ,  6 ) are formed as grating structures at the surface of a cover ( 4 ) being in contact with the waveguide ( 2 ). 
     
     
       10. Integrated-optical sensor according to  claim 1 , further comprising at least one phase modulator ( 24 ) for modifying the phase of at least one polarization direction of the sensing beam ( 12 ) and/or the reference beam ( 13 ). 
     
     
       11. Integrated-optical sensor, comprising:
 An optical waveguide ( 2 ) having at least a first incoupling region ( 3 ), wherein a sensing wave ( 14 ) is excited by a sensing beam ( 12 ), and a second incoupling region ( 5 ), wherein a reference wave ( 15 ) is excited by a reference beam ( 13 ), 
 at least one sensing area ( 4 ) located between the first ( 3 ) and the second ( 5 ) incoupling regions and passed through by the sensing wave ( 14 ), wherein a change of the propagation constant of the waveguide ( 2 ), and thus a phase shift of the sensing wave ( 14 ), occurs depending on the optical environment, 
 at least one detector ( 22 ) for measuring of an interference signal between the sensing wave ( 14 ) and the reference wave ( 15 ) 
 further comprising at least one phase modulator ( 24 ) for modifying the phase of at least one polarization direction of the sensing beam ( 12 ) and/or the reference beam ( 13 )
 wherein at least a part of the sensing wave ( 14 ) passes through the second incoupling region ( 5 ) after the sensing area ( 4 ), and the ratio of the amplitudes of the sensing wave ( 14 ) in front and behind the second incoupling region ( 5 ) is 20:1 at most, and 
 wherein the phase modulator ( 24 ) is formed as a liquid crystal element, which is controllable by an applied voltage, and comprising a first substrate with electrode ( 31 ), a second substrate with electrode ( 32 ), and a liquid crystal layer ( 30 ) in between. 
 
 
     
     
       12. Integrated-optical sensor according to  claim 11 , wherein the liquid crystal element comprises a nematic liquid crystal comprising no twist or a twist of less than 20°, and wherein at least one substrate ( 31 ) or ( 32 ) of the liquid crystal element causes a planar direction (r 1 , r 2 ) of orientation of the boundary liquid crystal molecules, thus defining the extraordinary axis of the liquid crystal element which is at least close to parallel to the associated light beam's polarization direction (pu) corresponding to the polarization of the wave excited in the waveguide ( 2 ). 
     
     
       13. Integrated-optical sensor according to  claim 12 , wherein furthermore a polarizer ( 34 ) is attached at least to the second substrate ( 32 ) in a region illuminated by a phase reference beam ( 17 ) generated by the lighting optics ( 23 ), and wherein the phase reference beam ( 17 ) is modulated in the intensity by the polarizer ( 34 ), and a phase reference detector ( 25 ) measures the intensity of the modulated phase reference beam ( 17 ′). 
     
     
       14. Integrated-optical sensor according to  claim 13 , wherein parasitic interferences originating from multiple reflections of sensing waves ( 14 ) are avoided, by placing the border edge of the cover ( 40 ), passed through by the sensing wave ( 14 ), askew at an angle between 5° and 45° with respect to the grating lines, or by illuminating the first and second incoupling regions ( 3 , 5 ) obliquely by the sensing beam ( 12 ) and reference ray ( 13 ) at an angle δ of greater than 5°, such as the sensing waves ( 14 ) and reference waves ( 15 ) propagate in a direction not perpendicular to the grating lines and the border edges of the cover ( 40 ). 
     
     
       15. Integrated-optical sensor according to  claim 11 , wherein at least one electrode ( 31 , 32 ) of the liquid crystal element comprises two independently controllable regions, wherein the first region ( 31 , 32 ) is illuminated by the sensing beam ( 12 ) and the second region ( 31 ′,  32 ′) is illuminated by the reference beam ( 13 ).